Mystery Rays Wow. Has to be the best blogging on real science I've ever seen. Enough reference to literature to satisfy the hard-core virologist, interesting and clear enough to appeal to the non-scientist.
Michael Palm HIV Basic Science Blog Totally hard-core HIV science.
Genomicron Fantastic genomics blog and distinctly Canadian perspective on science.
Laelaps, Tetrapodzoology, Deep Sea News These guys are zoologists and/or paleontologists. Which mean they're not only biologists, but they're also scientists. Which means as a biochemist, this is where I go for a reminder of the beauty of evolutionary theory and life in general. These guys make it all fun, interesting and easy to understand (lots of pictures too!!). They do a good bit of blogging on peer-reviewed research as well.
Cognitive Daily As advertised, "A new cognitive psychology article nearly every day". I don't know how they do it, but they do it.
Drug Monkey Lots of real science being thrown around here. More importantly, Drug Monkey has a sense of humor and this blog is damn fun to read.
Life of a Lab Rat Well-written tidbits of insight into laboratory culture.
Henry Some good stuff on human evolution.
CSHL Protocols General science and the latest in molecular biology methodology.
Sorry to the great blogs out there that I missed. Feel free to add your favorite science blogs to the list below.